Obstetric & gynaec radiology revision notes

Obstetric & gynaec radiology
TONY SCARIA 2010 KMC

Types of USG in O& G
Transabdominal USG for obstetric purposes 3-5 MHz
Trans vaginal USG for obstetric puposes 5-7.5 MHz
Transabdominal Transvaginal
Bladder should be full for transabdominal
scan as it creates good echo
Bladder should be empty

Timing of USG
First scan 7 weeks of gestation • Confirm pregnancy
• Exclude cardiac or molar
pregnancies
• Cardiac pulsation
• Measure CRL
Second scan (anomaly scan) 18-20 weeks • Look for congenital anomalies
Third scan 32 weeks or later • To assess fetal growth & fetal size

Diagnosis & confirmation of pregnancy by
USG
Gestational sac 4^1/2 weeks of gestation
Yolksac 5 weeks
Cardiac activity 6 weeks

Site of pregnancy
• Trans vaginal USG  IOC for unruptured ectopic pregnancies
• Absence of gestational sac in uterus
• Fluid in POD
• Extraovarial complex adnexal mass most sensitive & specific
• Pseudosac in uterus
• Tubal ring or echogenic ring  doughnut sign

Decidualisation in normal sac

Double decidual sign
• Normal USG appearance of
IU gestational sac
• Seen as 2 concentric
echogenic rings separated by
hyperechoic space

Pseudogestational sac

Ectopic pregnancy
• Unruptured ectopic is best detected by transvaginal USG

Fallopian tube in ectopic pregnancy
• d/t hypervascularity

Tubal ring or echogenic ring
• Non ovarian hypoechoic ring ring like mass
• Surrounded by fluid

Bagel sign in ectopic pregnancy
• Ultra sonographic sign of ectopic pregnancy
• Gestational sac in the adnexa with hyperechoic ring

Vaginal bleeding in early pregnancy
Viability can be assessed by cardiac activity
• Visible heart beat by pulsed Doppler @ around 6 weeks
• Clearly depicted by 7 weeks

Molar pregnancies
• Best diagnosed by USG
• Snow storm appearance
• Complete mole appears like
echogenic with numwerous
anechoic cyst like spaces

Snow storm appearance
• In hydatidiform mole
• Snow storm appearance in chest
• Mets from thyroid

Bunch of grapes sign in molar pregnancy

Diagnosis of fetal malformation
• Anomaly scan done @18-20 weeks
• Earliest anomaly which can be detected is anencephaly
• Detected@ 10-11 weeks
Signs in spina bifida
Lemon sign Compression or flattening of the
posterior cerebellar surface
making a crescentic appearance
Banana sign Concave deformity of the frontal
bones

Frog head appearance in anencephaly

Frod eye sign in anencephaly

Banana sign

Lemon sign

Gestational age assessment
1st trimester Crown Rump length (CRL)
2nd trimester Corrected biparietal diameter (cBPD) or head
circumference (HC)
3rd trimester Head circumference and femur length
• Crown rump length is the best
• Transcerebellar diameter (TCD) is an accurate predictor
of gestational age when measured between 14 and 28
weeks.

Fetal growth assessment
• Best indicator of fetal growth - Abdominal circumference
• best USG parameter to detect IUGR is Abdominal circumference
• best USG parameter to detect Macrosomia is Abdominal circumference

Butterfly sign
• Normal feature
• Normal appearance of choroid plexus on axial
imaging of fetal brain
• Absence of butterfly sign holoprosencephaly

TVS
• It is more informative in first trimester.
• In TVS images are of enhanced quality (5–7.5 MHz transducer).
• Full bladder is not required.
• It is superior to transabdominal USG in placenta previa.

• Use of transvaginal probe can detect the following events by one
week earlier then transabdominal.
• 1. Gestational ring - 5th week
• 2. Fetal poles - 6th week
• 3. Yolk sac - 6th week
• 4. Cardiac pulsation - 7th week
• 5. Embryonic movement - 8th week

T sign in monochorionic monoamniotic

λ(lambda sign) dichorionic diamniotic

Signs of intrauterine fetal death
• Spaldings sign
• Overlapping of sutural bone
• Roberts sign
• Air in great vessel& heart

Signs of IUD
Spalding sign Overlapping of sutural bines
Roberts sign Air in great vessels
Ball sign Crumpled up spine of fetus

Spalding sign

Normal umbilical A Doppler

Absent diastolic notch

Reversed end diastolic flow

Umbilical A Doppler
Systolic / diastolic ratio
< 2.5 Normal
>3.0 IUGR Decreased absent or reversal of
diastolic flow  impending fetal
demise
>3.5 in last trimester Terminate pregnancy

Uterine A Doppler

Normally diastolic notch disappears in late
trimester

• Persistent diastolic notch with
reduced diastolic flow in late
trimester  pregnancy induced
HTN

Middle cerebral A Doppler
Increased
pulsatility index
or increased
peak velocity
Fetal hypoxia
Fetal anemia
Fetal hydrops

Congenital uterine anomalies
• Best detected by MRI

Missing IUD
• USG
• IOC
• Hysteroscopy
• Locate & can be removed hysteroscopically
• Plain X ray

• ultrasound marker is associated
with greatest increased risk for
Trisomy 21 in fetus:
• Nuchal edema
• > 3mm

• Cystic hygroma in USG  turners syndrome

Obstetric & gynaec radiology revision notes

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Obstetric & gynaec radiology revision notes